The high school honors chemistry class for homeschoolers started today. First we went over what goes in the lab notebook. I had already asked the students to read the section on lab notebooks in the Standard/Honors Home School Chemistry Laboratory Kit CK01A Instruction Manual, by the Home Scientist so I just quickly went over the highlights. These lab books will be the proof that the student completed a LAB course and can be brought to college interviews to show that they did REAL labs, so its important they write down everything they do (procedure) and of course their data and results (good and bad). We also went over a bit of safety, I showed them where the fire extinguisher is kept and explained how to use it. Showed them the vinyl aprons we have to protect our clothes and asked the kids with long hair to pull it back to keep it out of chemicals and flames. I also plan on emailing them a MSDS, Material Safety Data Sheet, before class for each of the chemicals we will use that week and told them to note in their lab books any hazards they need to be aware of for that class.
The lab today was Separation of a Mixture found in Chapter 2 of Ian Guch’s 24 Lessons That Rocked the World. The students were each given a large spoonful of a mixture (photo on left) containing sand, salt and pepper and that they had to separate into its separate components. I had a variety of equipment out on the counter and told them to ask if there was something else they wanted to use. Many of the kids knew right off the bat that pepper would float, so they poured distilled water into their beaker containing the mixture. The pepper floated, the salt dissolved and the sand sunk to the bottom….for the most part. We didn’t use pure sand so we ended up with a few floaters from the sand as well, but for the most part it worked. The students skimmed off the pepper by pouring it carefully into a coffee filter in a funnel. Now they had to get the salt out of the water, so they poured some of the salt water into an evaporating dish or crucible and put it over a heat source. I have 3 heat sources, a hot plate, a wickless alcohol burner and a microburner (butane). Each one worked fine, though the microburner, in the photo below, was the most impressive and it was really nice being able to control the size of the flame, which you can’t do with the alcohol burner. The microburner was also very easy to fill. I may have to buy another one of those. One thing to watch out for is that when the water is almost gone the salt started splattering out of the cruicible and made a mess, so you may want to stop before it gets to that point.
Students put the filter papers with sand and pepper outside in the hot sun to evaporate the last of the water and the salt was left in the cruicibles. We ended up with brown salt and I challenged the students to figure out what was causing the color. When we poured water over the mixture the water turned brown, so it could have been the pepper or the sand tainting the water. Students took small samples of just sand and just pepper and put them in beakers with water. They found the pepper turned the water brown and the sand turned the water gray! This was when I remembered I had used the tray of sand for a different chemistry experiment a few years ago and that there was ash mixed in with the sand, hence the gray water and floaters from the sand.
If they finished the pepper mixture, they were challenged to try to separate a mixture of salt and sugar. One group used isopropyl alcohol and found that sugar dissolves in alcohol, but not salt! We all got a lesson in safety when they decided to get the sugar back by heating the alcohol over a burner. The resulting alcohol lamp they created when the liquid in the evaporating dish burst into flames was quite impressive and made one student exclaim, “This class is going to be so awesome!” Luckily there was only a little bit of isopropyl alcohol in the evaporating dish so the flame went out pretty quick, but I’m fairly certain all the students now know to keep alcohol away from the burners and they’ve all concluded this is going to be an exciting class. I was impressed that the kids all kept their cool and just stepped back, after turning off the microburner, to wait for the alcohol to burn up.
For homework this week I gave the kids some problems from Caveman Chemistry by Kevin M. Dunn. I had just enough time to go through the first problem before class ended, and asked the students to do some more of the problems at home to give them practice converting units. I haven’t read all of Caveman Chemistry yet, but its a unique approach in teaching chemistry along with some basic skills, like making fire with a bow drill, flint knapping and making mead. The author also has a good sense of humor so its an entertaining read so far.
Before class I had asked kids to read Chapter 1 in Modern Chemistry textbook and/or watch Crash Course Chemistry 1 and 2.
Or if they prefer Tyler Dewit, he has some videos on unit analysis.